Sal,
I've got some questions for you about your rig set-up. I've wanted to make one of these for quite awhile, but never got around to it. Recently, though, I've been working on several Alco sets (early, heavy ones) and decided to add a motor to the dummy unit to improve their pulling power. To put it mildly, it's pretty dramatic. But I wanted to quantify it with a drawbar test rig. So, I ordered the digital scale I mentioned above and this week I constructed a test track. The scale itself is very accurate (I've weighted several reference objects to determine that). But I'm not getting results close to what you've charted and I'm not sure why.
My test track is a new 36 inch 027 track (since upgraded to a bit longer to accommodate the Alcos). The attachment for the scale is similar to yours, but I'm not sure about the connection to the engines. I started out using a piece of wire (wrapped around the scale hook and then the coupler). I experimented with a spare truck (but unfortunately, it's not as free rolling as I'd like). The directions for the scale point out that anything added to the hook will throw off the accuracy and you have to use the tare function to compensate. So, I have a feeling that the addition of the extra truck and connections to the engines might be accounting for our differences in results. I've been testing mostly PW engines, but I got a red flag when I put my Williams FM Trainmaster on the track. That thing is a real stump puller, but I did not get a high reading for it and I got wheel slip (even though it has traction tires). How exactly are you connecting your engines to the scale? I'm trying to figure out why your readings are so much higher than I'm getting. One thing is for sure......my PW engines are all great runners. I'm kind of obsessive about that. When I get a "new" engine or set (like the Alcos) I work on them until they run like silk and if I think the magnetraction is weak in a truck, I quickly replace it with a strong one. So, I don't think the differences lie in the mechanical condition of the engines.
Roger
